1. Field of the Invention
The present invention generally relates to a plasma processing method.
2. Description of the Related Art
In a process of manufacturing a semiconductor device, fine patterns are formed on a substrate (e.g., semiconductor wafer) by using a plasma etching process. In a case of using the plasma etching process, a target etching material provided on the substrate and a reaction gas used for plasma etching cause a reaction, and a reaction product may accumulate mainly at a sidewall part of an etched pattern.
The reaction product may serve as a protection film that prevents the sidewall part of the etched pattern from being etched during the plasma etching process. On the other hand, if a subsequent process for forming a CVD (Chemical Vapor Deposition) film, a wiring or the like is performed in a state where the reaction product is left remaining, the remaining reaction product may lead to the formation of particles or defective wirings. Therefore, a reaction product that remains mainly at a sidewall part of a pattern is to be removed.
For example, Japanese Laid-Open Patent Publication No. 2007-73840 discloses a technology pertaining to a method for removing a reaction product in which ashing is performed by using oxygen plasma after wet-etching a patterned substrate with a hydrofluoric acid solution and covering an entire surface including an etching surface with an organic material film containing OH or H.
However, by performing a wet-etching process on a substrate by using the hydrofluoric acid solution, not only is the reaction product accumulated mainly at the sidewall part of a pattern is removed by the wet-etching but also an underlayer formed on the substrate is also etched. Therefore, the underlayer may become damaged.